A graphics engine, graphics processing unit (GPU), or visual processing unit (VPU), is a specialized electronic circuit designed to rapidly manipulate and alter memory to accelerate the creation of images in a frame buffer typically intended for output to a display. GPUs may be found in embedded systems, mobile phones, tablets, notebook computers, high performance computation (HPC) servers, and game consoles. In addition to manipulating computer graphics in particular, a highly parallel architecture also enables a GPU to more generally perform processing of large blocks of data in parallel.
While many of the processing activities handled by a GPU are computationally intensive, there is an increasing need for energy efficient GPU architectures capable of scaling performance/watt not only between form factors (e.g., HPC server vs. a smartphone), but also dynamically within a particular form factor to handle different workloads at different times. For example, in an interactive usage application executing on a smartphone, such as opening a set of photos in response to a user action, a power-level of an embedded GPU may be ramped up (i.e., a graphics turbo mode) for a few milliseconds-seconds to provide a fast user experience. Such a turbo mode may dissipate significantly higher power during this short duration than over longer sustained workloads as generally limited by junction temperature. Depending on the thermal design power (TDP) for the given platform, GPU sustained power dissipation may be restricted to no more than 1-2 W in an exemplary tablet form factor, or a few hundred milliwatts in a smartphone form factor. Furthermore, limited battery resources of a mobile device may impose additional limitations on power dissipation to ensure that the device can function for the longest possible time.
Processor architectures and operational modes that facilitate power management in a manner that can enhance the power-performance point of the processor, improve user perception of performance, and offer greater operational flexibility are advantageous.